Fluid systems that urge a fluid to flow from one location to another are well known. The fluid in some fluid system applications may flow through an area exposed to freezing temperatures that may cause the fluid to freeze and block fluid flow. For example, solar water heating systems utilize a pump that urges water to flow through supply pipes extending between a solar heating assembly that heats the water by solar energy and a hot water tank that stores the heated water. The supply and return pipes, however, may be exposed to outdoor temperatures below freezing that cause the water in the supply pipes to freeze and prevent operation of the heating system.
Some users of solar water heating systems manually monitor the system for water freezing in the supply pipes and turn on heaters wrapped around the pipes as needed to melt the ice blocking the pipes, and then turn off the heaters well after the blockage is cleared. Requiring manual intervention and supervision of the hot water heating system is often impractical, particularly in residential applications where the homeowner may be away. Energy is wasted if the heaters are kept on longer than necessary.
Some conventional solar water heating systems avoid the problem of water freezing in the supply lines by draining the water from the pipes when freezing may occur. This increases system complexity and prevents use of the system during cold months. Other conventional solar heating systems replace water with another fluid, such as ethylene glycol, that does not freeze when exposed to outdoor temperatures. This solution is less energy efficient and is considerably more complicated and expensive than solar heating systems that use water as a heat transfer medium.
Accordingly, there is a need for an improved method for automatically initiating the flow of fluid through a pipe or the like in which a portion of the pipe may be exposed to freezing temperatures such that fluid flow through the pipe may potentially be blocked by frozen fluid in the pipe. The method should be relatively inexpensive to implement, not require manual intervention, and be relatively energy-efficient in clearing the blockage. The improved method should be useable with solar hot water heating systems.